As for “La tua risposta è di grande aiuto a me”, it is nothing but the literal translation of the English sentence “Your answer is very helpful to me” which however is not acceptable in Italian .

To sum up, it is not acceptable to use both the indirect object pronoun “mi” and the stressed pronoun “a me” to express “to me” in the example that you mention and then the method more correct is to use the indirect object pronoun “mi” instead of the stressed pronoun “a me”.